The medial collateral ligament (MCL) is one of four ligaments that are critical to the stability of the knee joint. A ligament is made of tough fibrous material and functions to control excessive motion by limiting joint mobility. The four major stabilizing ligaments of the knee are the anterior and posterior cruciate ligaments (ACL and PCL, respectively), and the medial and lateral collateral ligaments (MCL and LCL, respectively).
The MCL spans the distance from the end of the femur (thigh bone) to the top of the tibia (shin bone) and is on the inside of the knee joint. The medial collateral ligament resists widening of the inside of the joint, or prevents "opening-up" of the knee.
Grade I MCL Tear
This is an incomplete tear of the MCL. The tendon is still in continuity, and the symptoms are usually minimal. Patients usually complain of pain with pressure on the MCL, and may be able to return to their sport very quickly. Most athletes miss 2-4 weeks of play.
Grade II MCL Tear
Grade II injuries are also considered incomplete tears of the MCL. These patients may complain of instability when attempting to cut or pivot. The pain and swelling is more significant, and usually a period of 4-6 weeks of rest is necessary.
Grade III MCL Tear
A grade III injury is a complete tear of the MCL. Patients have significant pain and swelling, and often have difficulty bending the knee. Instability, or giving out, is a common finding with grade III MCL tears. A knee brace or a knee immobilizer is usually needed for comfort, and healing may take 6 weeks or longer.